This application is submitted to NIDA in response to RFA-DA-04-006, Screening and Intervention for Youth in Primary Care Settings, and proposes a controlled trial of an primary care office intervention for adolescent substance abuse that includes computerized screening, brief provider advice, and parent and adolescent education. Use of drugs is associated with a variety of health care problems, making settings where adolescents receive routine medical care ideal for implementation of routine screening and early intervention. However, medical settings are currently underutilized in this regard and new evidence-based strategies are needed to improve practice patterns, including standardized methods of screening, assessment, brief intervention, and referral to treatment. We have previously conducted studies aimed at assessing the reliability of substance abuse screening tests in primary care settings that serve adolescents. We then developed a new brief screen, the CRAFFT, which is both developmentally appropriate for adolescents and practical for use in busy clinic settings. We are currently conducting a study of screening implementation with the CRAFFT test in a network of primary care sites in New England that includes an adolescent clinic, pediatric practices, family practices, and school-based health centers. As part of this study we have developed and pilot tested a computerized CRAFFT screening program, which will deliver adolescent feedback and provider prompts that are tailored to the adolescent's level of substance use involvement. The next logical steps in our research are to develop a demonstration video and provider training protocol, supplementary parent and adolescent education materials, and then to conduct an efficacy trial of the comprehensive screening and brief advice approach within our practice-based research network. Year one of the proposed study will be used for "wash out" of our current screening study, production of a demonstration video and provider training protocol that are practical for busy offices, and conducting focus groups with parents and adolescents. During years 2-4 we will test the efficacy of the approach using a pretest posttest controlled experimental design. The experimental and control cohorts will be recruited sequentially at all participating sites. Pretests will be given at the time of the annual well care visit, and posttest observations will be obtained at 3-months and 12-months following study entry. We will assess outcome by measuring between-groups differences in rates of substance use cessation among users, and differences in substance use initiation among non-users. We will also track primary care provider's management strategies and adolescents' adherence with follow-up appointments. An effective brief intervention could be widely implemented in primary care practices that serve adolescents, and would be of enormous public health significance across the U.S.